Fig. 2: Characterization and rectification behavior of the chemically gated artificial nanochannels.

a Schematic illustration showing the procedure of modification at the inner surface of the nanopipettes. Step 1: piranha treatment to obtain hydroxyl groups. Step 2: 3-aminopropyl-triethoxysilane (APTES) treatment to induce amino groups. Step 3: glutaraldehyde (GA) treatment to form electrically neutral aldehyde groups. Step 4: modification of amino group-labeled Seq-1/Seq-2 dimers. b SEM images of nanopipettes after modification. Left: top view. Right: side view. c Current–voltage (I–V) curves measured in a single nanopipette at different steps of the modification procedure. d Zeta potentials measured at different steps of the modification procedure. Here, silica nanoparticles were used to simulate the inner wall of the nanopipettes to perform the same modification procedure in (a). e Schematic illustration of the single-input/single-output (SISO) model. f SISO operation in the chemically gated artificial nanochannels. Input from left to right: Ca²⁺, ROS, H⁺. Output from left to right: I, II, III. g Rectification ratio measured in nanopipettes modified by Seq-1/Seq-2 upon the addition of different metal ions (Cu²⁺, Ba²⁺, Zn²⁺, Mg²⁺, Na⁺, Ag⁺, Fe³⁺ and all the metal ions were 2 µM). h Current–voltage (I–V) curves measured in the chemically gated artificial nanochannels before and after single-input stimuli corresponding to (f). Inset: ICR ratios corresponding to the I–V curves. Error bars in (c, d, g, h) represent the standard deviation of three independent experimental repeats, and the measure of the center represents their corresponding mean value. Significance of the ICR ratio was assessed by t-test (n = 3 independent experiments and the data were presented as the mean values ± SDs, *p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001). All statistics were calculated using two-tailed paired t-tests. Source data are provided as a Source data file.